Neonatal Mortality for Primary Cesarean and Vaginal Births to Low-Risk Women: Application of an “Intention-to-Treat” Model

Rates of cesarean delivery continue to increase substantially in the United States, even in women thought to be at low risk for the procedure. This study used an “intention-to-treat” approach, recommended by a National Institutes of Health conference, to assess the neonatal mortality risk according to method of delivery in low-risk women. Participants had singleton, term (37–41 weeks’ gestation) fetuses in vertex presentation, no reported medical risk factors, and no placenta previa or previous cesarean section. The study population included 8,026,415 births and 17,412 infant deaths. A “planned vaginal delivery” category combined vaginal births with cesarean deliveries associated with labor complications or procedures. This group was compared with a “planned cesarean delivery” category that included cesarean deliveries without labor complications or procedures. Multivariable logistic regression analysis was used to model neonatal mortality as related to method of delivery while adjusting for sociodemographic and medical risk factors. The neonatal mortality rate was 0.63 for vaginal deliveries and 1.69 for primary cesarean deliveries with labor complications or procedures. The overall rate for the planned vaginal delivery group was 0.72. The nonadjusted neonatal mortality rate for primary cesarean deliveries with no reported labor complications or procedures was 1.73–2.4 times the rate for the planned vaginal delivery group. Based on logistic regression analysis and the most conservative model, the adjusted odds ratio for neonatal mortality was 1.69 (95% confidence interval, 1.35–2.11) for cesarean deliveries with no labor complications or procedures, compared with planned vaginal deliveries. Considering the rapid increase in primary cesarean deliveries without medical indications, the finding that cesarean deliveries with no labor complications or procedures pose a 69% greater risk of neonatal mortality than does planned vaginal delivery is of considerable importance.